1-D Modeling of Hydrate Depressurization in Porous Media

A thermal, three-phase, one-dimensional numerical model is developed to simulate two regimes of gas production from sediments containing methane hydrates by depressurization: the dissociation-controlled regime and the flow-controlled regime. A parameter namely dissociation-flow time-scale ratio, Rτ, is defined and employed to identify the two regimes. The numerical model uses a finite-difference scheme; it is implicit in water and gas saturations, pressure and temperature, and explicit in hydrate saturation. The model shows that laboratory-scale experiments are often dissociation-controlled, but the field-scale processes are typically flow-controlled. Gas production from a linear reservoir is more sensitive to the heat transfer coefficient with the surrounding than the longitudinal heat conduction coefficient, in 1-D simulations. Gas production is not very sensitive to the well temperature boundary condition. This model can be used to fit laboratory-scale experimental data, but the dissociation rate constant, the multiphase flow parameters and the heat transfer parameters are uncertain and should be measured experimentally.